High-power chemical lasers such as Chemical Oxygen-Iodine Lasers have been proposed for various military applications and other industrial applications. In chemical lasers, chemical reactions are used to produce exited atoms or molecules in a flow of suitable mixture of rarefied gases. Gas containing excited species is flowed through a laser cavity or resonator where optical energy is extracted from the excited species by means of an optical resonator. Required flow throughput and pressure are produced by vacuum pumps which draw the gas mixture through the laser cavity. High-energy chemical lasers for military applications often produce hundreds of kilowatts of optical power. The corresponding gas throughput in the range of 10–100 Torr pressure requires vacuum pumps with pumping speeds on the order of several hundred thousand liters per second. Military applications for high-power chemical lasers include tactical air defense which necessitates deployment of laser weapons in forward positions on the battlefield. Such laser weapons must be transportable and, therefore, of limited size and weight. In addition, the laser weapon should be concealable and undetectable by the enemy.
High-energy chemical lasers can be classified as either 1) hydrogen-halide or 2) Chemical Oxygen-Iodine Laser (COIL). Hydrogen-halide lasers typically involve a reaction of hydrogen and/or deuterium with fluorine, chlorine, bromine or iodine in diluent gases of nitrogen, helium, or alike, to produce hydrogen and/or deuterium halide molecules in excited vibrational states from which laser energy can be extracted. Exhaust from the laser cavity of a hydrogen-halide laser is typically a mixture of gases at high temperature (up to 1000 degrees Centigrade) including HF (and/or DF), N2, and possibly small amounts of H2 (and/or D2), O2 and H2O.
On the other hand, COIL lasers typically involve reaction of chlorine in diluent gases such as nitrogen or helium, with aqueous solution of alkaline hydrogen peroxide to produce intermediate excited specie known as singlet delta oxygen. Singlet delta oxygen is subsequently mixed with iodine vapor to generate iodine atoms in electrically excited state and suitable for extraction of laser energy. Exhaust from a COIL laser cavity is typically a mixture of gases at near ambient temperature including nitrogen or helium and oxygen with small amounts of chlorine, iodine, and water.
The laser cavity or gain region is typically separated from the resonator boxes using an isolation valve and a flow straightening optical tunnel on either end of the cavity region. The overall length, the two valves, and two tunnels increase the mass of the system. Such systems may be employed in transportable-type systems, such as but not limited to airplanes, ground-vehicle mounted, or sea-based. Reducing the mass of transportable-type systems is a desirable goal. It should be also noted that these systems are mounted to a bench or fixture. The length of the bench must be the sum of the length of the laser cavity plus the resonator boxes lengths plus the lengths of the optical tunnels and the isolation valves. Such systems also include a vacuum pump and purge gases that are used to create a positive pressure in the resonator boxes so that flow direction of the gases is out of the box through the cavity and diffuser and the gases do not back flow into the resonator boxes. It should be noted that back flow of the laser cavity exhaust may cause caustic damage to the precision optics inside the resonator boxes. It also should be noted that the optical isolation valves completely block the line of sight of the lasers when not open. The closed valve prevents the monitoring of the optics within the boxes thereby limiting the ability to make the as-required adjustments to the optics for alignment of the laser optical resonator. Each valve has an associated actuator system that also increases the mass of the laser system.
It would therefore be desirable to reduce the mass of a laser system to be suitable for use in a mobile-based or transportable-type system.
It would therefore also be desirable to have a low mass means of preventing laser cavity exhaust back flow into the optical enclosures.
It would therefore be desirable to provide a low mass means of unobstructed inter-optical enclosure line-of-sight that facilitates optical resonator alignment.